Mean pulmonary venous pressure (= LAP = [[2023-NOV-GM#Pulmonary capillary wedge position and pressure| Wedge Pressure]]) = 5mmHg.

Muscarinic receptors

Muscarinic receptors are G-coupled protein receptors involved in the parasympathetic nervous system.
The only exception to this rule are the receptors is the sweat glands, which possess muscarinic receptors but are part of the sympathetic nervous system. Source
Mnemonic: Musca-para-Gee

• Absence of phaeochromocytoma or myocarditis.

L-dopa -> Dopamine -> Norad -> adrenaline -> ?waste products

| Phentolamine | Non selective alpha adrenergic blocker; | Used in catecholamine induced hypertension (phaeochromocytoma, tyramine ingestion in patient on MAOI |

Multiple Endocrine neoplasia syndromes

Pulmonary capillary wedge position and pressure (PCWP)

#2023GM-NOV/Q02
Pressure transduced catheter is introduced into the femoral or jugular vein.

Basic Science

Source

• Then advanced through SVC/ IVC -> right atrium -> Right ventricle -> Pulmonary artery -> Left or right branch PA.
• Position can be confirmed by the pressure tracing in each position.
• Inflation of the balloon blocks off the branch PA -> after a few seconds, pressure distal to the balloon approximates left atrial pressure.
• Ideally, the catheter tip should be in an arterial segment supplying a "[[2018-OCT-BSQ#Pulmonary vascular resistance|Zone 3]]" region of the lung. (Alveolar pressure is less than PA and PV pressure so that blood stream from PA to PV is uninterrupted -> pressure is transmitted from LA to catheter port)

Clinical context

• Clinical Use:
  • Diagnosis of severity of left ventricular failure
  • quantify degree of mitral valve stenosis
  • AS, AR, MR also ⬆ LA Pressure
  • Measurement of cardiac output by thermodilution.
  • Calculation of pulmonary vascular resistance (based on measurement of pulmonary blood flow, pulmonary artery pressure and PCWP)
• Values: Pulmonary oedema likely above PCWP > 20mmHg.
• Complications: Pulmonary artery rupture from over inflation of the balloon.
• Pitfalls: Proper placement is essential for accurate results:
  • Placement is confirmed by Source
    • Presence of well defined a and v waves.
    • Fluoroscopic confirmation of position
    • Oxygen saturation > 90%
      • In the proper wedge position with complete occlusion, saturation should approximate left atrial saturation (i.e > 90%). Lower saturation indicates incomplete occlusion by the balloon. Source
    • Abrupt rise in mean pressure when the balloon is deflated.

Phaeochromocytoma

Basic Science

• Tumour of adrenal medulla which secretes catecholamines (Adrenaline and noradrenaline).
• [[Hormone Physiology#Adrenaline synthesis]]
• Extradrenal tumours (paragangliomas) produce mainly noradrenaline. Others produce both. [[2020-BasicSciences-July#Autonomic nervous system and organization]]
  • See [[2022 November SBR#Beta blocker pharmacology]]
    [[adrenoceptors.png]]

Clinical context

• A Very rare cause of hypertension
• Presentation: Continous OR intermittent symptoms. Can cause sudden death! -> patients with phaeochromocytoma must be investigated.
  • Symptoms include the obvious ones as well as flushing / pallor, constipation or diarrhoea and Raynaud's phenomenon, polyuria and nocturia, glycosuria, orthostatis hypotension.
• Associations: [[2022-November#Multiple Endocrine neoplasia syndromes|MEN2]], VHL and neurofibromatosis.
• 25% are multiple, 10% malignancy risk.
• Confirmation of diagnosis:
  • Three Negative 24 hour urinary metanephrine levels excludes the diagnosis. -> so used as a screening test.
  • Dietary vanilla inteferes!
  • 
  • Testing sequence: Screening as above -> plasma metanephrines , Plasma chromogranin A, Clonidine suppresssion test -> +/- Imaging (MRI, MIBG uptake scans, PET) -> genetic testing upon confirmation.